Digital Signal Processing Reference
In-Depth Information
share the same bandwidth. Modern cell phone techniques, such as CDMA (Code Division Multiple
Access) rely heavily on advanced, digitally-based signal processing techniques to efficiently achieve both
high quality and high security.
1.3 DSP NOMENCLATURE AND TOPICS
Figure 1.2 shows a broad overview of digital signal processing. Analog signals enter an ADC from the
left, and samples exit the ADC from the right, and may be 1) processed strictly in the discrete time
domain (in which samples represent the original signal at instants in time) or they may be 2) converted
to a frequency domain representation (in which samples represent amplitudes of particular frequency
components of the original signal) by a time-to-frequency transform, processed in the frequency domain,
then converted back to the discrete time domain by a frequency-to-time transform. Discrete time domain
samples are converted back to the continuous time domain by the DAC.
Note that a particular signal processing system might use only time domain processing, only
frequency domain processing, or both time and frequency domain processing, so either or both of the
signal processing paths shown in Fig. 1.2 may be taken in any given system.
Discrete Time Domain
Analog
Input
Time Domain
Proc
e
ssing
Analog
Output
ADC
DAC
Time to
Frequency
Transform
Frequency
to Time
Transform
Frequency Domain
Processing
Discrete Frequency Domain
Continuous
Time Domain
Continuous
Time Domain
Figure 1.2:
A broad, conceptual overview of digital signal processing.
1.3.1 TIME DOMAIN PROCESSING
Filtering, in general, whether it is done in the continuous domain or discrete domain, is one of the
fundamental signal processing techniques; it can be used to separate signals by selecting or rejecting
certain frequencies, enhance signals (such as with audio equalization, etc.), alter the phase characteristic,
and so forth. Hence a major portion of the study of digital signal processing is devoted to digital filtering.
Filtering in the continuous domain is performed using combinations of components such as inductors,
capacitors, resistors, and in some cases active elements such as op amps, transistors, etc. Filtering in
the discrete or digital domain is performed by mathematically manipulating or processing a sequence
